Superabsorbent polymer (SAP) is synthetic polymer material that can absorb moisture of 500 to 1000 times of self-weight, and is also named differently as super absorbency material (SAM), absorbent gel material (AGM), etc. according to developing companies. The superabsorbent polymer began to be commercialized as sanitary items, and currently, it is being widely used as hygienic goods such as a disposable diaper and so on, water-holding material for soil, water stop material for civil engineering and architecture, sheets for raising seedling, freshness preservatives in the field of food circulation, and so on.
In most cases, such superabsorbent polymer is widely used in the field of hygienic products such as a diaper or a sanitary pad, etc., and for this purpose, it is required to exhibit a fast absorption speed for moisture, etc., and to exhibit absorption speed above a certain level even under external pressure.
Particularly, with the thinning of hygienic products such as a diaper or a sanitary pad, etc., higher absorption performance is required for superabsorbent polymer. Above all, it is an important problem on the rise to improve permeability and absorption speed together, the conflicting properties of superabsorbent polymer, so that body liquid may be rapidly spread in the hygienic product, and simultaneously, may be absorbed fast.
Thus, there is an attempt to improve permeability of superabsorbent polymer by allowing inorganic particles such as silica, etc. to exist between superabsorbent polymer particles so as to improve permeability and absorption speed of superabsorbent polymer together.
However, in case large quantities of inorganic particles are used for sufficient improvement in permeability of superabsorbent polymer, the absorption speed was rather lowered under pressure. And, the inorganic particles added to the superabsorbent polymer in the processes of grinding and sieving of superabsorbent polymer were separated, and thus, it was difficult to expect improvement in permeability to a desired level.
Therefore, there is an urgent demand for the studies on the improvement in permeability and absorption speed of superabsorbent polymer without causing the above described problems.